Feasibility of 68Ga-FAPI-46 PET for evaluating active fibrosis in aortic aneurysm

Aortic aneurysm (AA) is a disease where aortic wall loses its elasticity, showing fibrosis. Fibroblast activation protein (FAP) expression can be evaluated using radiolabeled FAP-inhibitor (FAPI) PET in fibrosis. We investigated FAP expression in AA and the feasibility of 68Ga-FAPI PET for AA imaging. Twenty AA patients who were planned for resection were prospectively enrolled. Nine lung cancer patients were used as control. Markers including FAP expression were assessed in AA and the remote aorta. Preoperative 68Ga-FAPI-46 PET was evaluated visually and quantitatively using maximal standard uptake value (SUVmax), and were compared with the growth rate of AA. FAP expression was increased in Western blotting (P = 0.014), both in intima and adventitia of AA. The SUVmax was significantly correlated with the FAP expression (r = 0.678, P = 0.008). The SUVmax of AA was significantly higher than the aortic SUVmax of the control (P = 0.018). The growth rate of AA was different between the uptake grade groups (P = 0.029), and correlated with SUVmax (r = 0.625, P = 0.013). FAP expression is variably increased in AA and possibly related to the progression of AA. 68Ga-FAPI PET can be a promising imaging for evaluating FAP expression of AA.